2,525 research outputs found
SO(10) and Large nu_mu - nu_tau Mixing
A general approach to understanding the large mixing seen in atmospheric
neutrinos is explained, as well as a highly predictive SO(10) model which
implements this approach. It is also seen how bimaximal mixing naturally arises
in this scheme. (Talk presented at NNN99, SUNY Stony Brook, Sept. 22-26, 1999)Comment: 10 pages, LaTe
Explicit SO(10) Supersymmetric Grand Unified Model for the Higgs and Yukawa Sectors
A complete set of fermion and Higgs superfields is introduced with
well-defined SO(10) properties and U(1) x Z_2 x Z_2 family charges from which
the Higgs and Yukawa superpotentials are constructed. The structures derived
for the four Dirac fermion and right-handed Majorana neutrino mass matrices
coincide with those previously obtained from an effective operator approach.
Ten mass matrix input parameters accurately yield the twenty masses and mixings
of the quarks and leptons with the bimaximal atmospheric and solar neutrino
vacuum solutions favored in this simplest version.Comment: Published version appearing in PRL in which small modifications to
original submission and a paragraph concerning proton decay appea
Realization of the Large Mixing Angle Solar Neutrino Solution in an SO(10) Supersymmetric Grand Unified Model
An SO(10) supersymmetric grand unified model proposed earlier leading to the
solar solution involving ``just-so'' vacuum oscillations is reexamined to study
its ability to obtain the other possible solar solutions. It is found that all
four viable solar neutrino oscillation solutions can be achieved in the model
simply by modification of the right-handed Majorana neutrino mass matrix, M_R.
Whereas the small mixing and vacuum solutions are easily obtained with several
texture zeros in M_R, the currently-favored large mixing angle solution
requires a nearly geometric hierarchical form for M_R that leads by the seesaw
formula to a light neutrino mass matrix which has two or three texture zeros.
The form of the matrix which provides the ``fine-tuning'' necessary to achieve
the large mixing angle solution can be understood in terms of Froggatt-Nielsen
diagrams for the Dirac and right-handed Majorana neutrino mass matrices. The
solution fulfils several leptogenesis requirements which in turn can be
responsible for the baryon asymmetry in the universe.Comment: 14 pages including 2 figure
Lepton Flavor Violation in Supersymmetric SO(10) Grand Unified Models
The study for lepton flavor violation combined with the neutrino oscillation
may provide more information about the lepton flavor structure of the grand
unified theory. In this paper, we study two lepton flavor violation processes,
and , in the context of supersymmetric SO(10)
grand unified models. We find the two processes are both of phenomenological
interest. In particular the latter may be important in some supersymmetric
parameter space where the former is suppressed. Thus, Z-dacay may offer another
chance for looking for lepton flavor violation.Comment: 26 pages, 10 figure
Bound-State Model of Weak and Strong Interactions
The pion-nucleon coupling constant is calculated from first principles by use of the N/D matrix method. Three models are introduced which contain pions, nucleons, and weakly interacting intermediate bosons of the scalar, pseudoscalar, and vector variety. The basic interactions are taken to be parity and isotopic spin conserving. Certain physical assumptions in the nature of boundary conditions and the known fact that the weak coupling is very weak, together with use of the Born approximation for N, enable us to obtain an eigenvalue equation which expresses the pion-nucleon coupling constant in terms of the three masses in the problem. The correct value for gπ^2 can be obtained for an intermediate vector meson of mass comparable to the nucleon mass with essentially no cutoff employed; on the other hand, the experimental value is also obtained with a spin-zero boson and a relatively small cutoff energy
Resonant leptogenesis in a predictive SO(10) grand unified model
An SO(10) grand unified model considered previously by the authors featuring
lopsided down quark and charged lepton mass matrices is successfully predictive
and requires that the lightest two right-handed Majorana neutrinons be nearly
degenerate in order to obtain the LMA solar neutrino solution. Here we use this
model to test its predictions for baryogenesis through resonant-enhanced
leptogenesis. With the conventional type I seesaw mechanism, the best
predictions for baryogenesis appear to fall a factor of three short of the
observed value. However, with a proposed type III seesaw mechanism leading to
three pairs of massive pseudo-Dirac neutrinos, resonant leptogenesis is
decoupled from the neutrino mass and mixing issues with successful baryogenesis
easily obtained.Comment: 22 pages including 1 figure; published version with reference adde
Texture of fermion mass matrices in partially unified theories
We investigate the texture of fermion mass matrices in theories with partial
unification (for example ) at a scale
GeV. Starting with the low energy values of the masses and the
mixing angles, we find only two viable textures with atmost four texture zeros.
One of these corresponds to a somewhat modified Fritzsch textures. A
theoretical derivataion of these textures leads to new interesting relations
among the masses and the mixing angles.Comment: 10 pages(Latex
`t Hooft Anomaly Matching for QCD
I present a set of theories which display non-trivial `t Hooft anomaly
matching for QCD with flavors. The matching theories are non-Abelian gauge
theories with "dual" quarks and baryons, rather than the purely confining
theories of baryons that `t Hooft originally searched for. The matching gauge
groups are required to have an dimensional representation. Such a
correspondence is reminiscent of Seiberg's duality for supersymmetric (SUSY)
QCD, and these theories are candidates for non-SUSY duality. However anomaly
matching by itself is not sufficiently restrictive, and duality for QCD cannot
be established at present. At the very least, the existence of multiple anomaly
matching solutions should provide a note of caution regarding conjectured
non-SUSY dualities.Comment: 8 pages, LaTeX, version to be published in PR
A Predictive Minimal Model for Neutrino Masses and Mixings
A model is considered in which the scale of the heavy singlet neutrinos is a
few orders of magnitude below the grand unification scale and where
right-handed vector bosons play still a negligible role. In a basis with
diagonal up-quark and Dirac-neutrino mass matrices it is assumed that the heavy
neutrino mass matrix has only zero elements in its diagonal, in analogy to the
light neutrino mass matrix in the Zee model. Connecting then the remaining
matrix elements with the small parameter describing the hierarchy of quark
masses and mixings and by assuming commutativity of the charged lepton with the
down-quark mass matrix, the calculation of all neutrino properties can be
performed in terms of the two mass differences relevant for atmospheric and
solar neutrino oscillations. CP-violation is directly related to CP-violation
in the quark sector.Comment: revtex, 9 pages, two references added, to be published in Phys. Rev.
D presented at Neutrino' 2000, Sudbury, Canad
Antisymmetric Higgs representation in SO(10) for neutrinos
A Model based on SO(10) grand unified theory (GUT) and supersymmetry is
presented to describe observed phenomena for neutrinos. The large mixing angles
among different generations, together with the small masses, are attributed to
the Higgs boson structure at the GUT energy scale. Quantitative discussions for
these observables are given, taking into account their energy evolution.Comment: 10 page
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